The present invention relates to a novel process for the removal of sulfur compounds from petroleum distillates by selective adsorption on activated carbon which can be used in petroleum refining for the desulfurization of gasoline, naphtha, kerosene, diesel fuel, fuel oil and other products.
The production of sulfur-free petroleum distillates is becoming more and more important due to environmental concerns. In particular, diesel fuel is now regulated all over North America to a maximum sulfur level of 500 ppm (Federal Register, Vol. 64, No. 92, May 13, 1999) for highway diesel engines. In Europe and Japan sulfur levels down to 50 ppm or even lower have been proposed. Currently, catalytic hydrodesulfurization is the technology that is practiced in refineries to reduce diesel sulfur to 500 ppm. The high pressures and temperatures associated with hydrodesulfurization and modifications thereof not only significantly increase the cost, they also have the potential to alter desirable characteristics of distillate fuels. Therefore, there is both a strong economic and technical incentive to develop cost effective techniques for sulfur reduction using very mild conditions (e.g., 20xc2x0 C. to 75xc2x0 C. temperature and ambient to very low pressures).
U.S. Pat. No. 5,454,933 teaches a process that uses activated carbon together with catalysts composed of Group VI and Group VIII metals as a polishing desulfurization agent for distillates previously subjected to hydrodesulfurization. U.S. Pat. No. 2,877,176 teaches the use of alkali-doped activated carbon for adsorption of sulfur from distillate fuels followed by washing the carbon with a hot hydrocarbon. However, a complete process for economic sulfur removal by an adsorbent using negligible amounts of activated carbon (impregnating a catalyst within the carbon to create its activation) and other reagents which results in reduced emissions into the environment is not disclosed or described in the prior art.
The present invention relates to a process for desulfurization of petroleum distillates, in particular diesel fuel separated by distillation into a low sulfur and a high sulfur fraction, using cyclic low temperature adsorption of the high sulfur diesel fraction on commercially available activated carbon (catalytically impregnated carbon) followed by a solvent stripping step, a regeneration (solvent-washing) step and a carbon drying step in a closed loop zero emission system. The desulfurized diesel fuel is then blended with the low-sulfur diesel fraction from the primary crude separation (distillation) step to yield the final desulfurized diesel product and a high-sulfur by product.
It is an object of the present invention to reduce total sulfur levels in petroleum distillates to less than approximately 500 ppm.